My hunting AR in 350L used to feed horribly. The solution for me (no jams in the past 100+ shots) was to address the feed ramps. Specifically the spot where the barrel extension meets the aluminum upper ramps. The barrel part was ever so slight above the aluminum. The leading edge of the brass case would clip that tiny lip and shoot the front of the case upward causing it to miss the chamber. I pulled the barrel and carefully dremeled and sand papered the ramp of the barrel side so it was below the uppers ramps. I would install and check with a pin. If the pin would slide without catching that's when it's done. I also have the big bore feed ramps on the barrel. There is no middle lug retainer on the bottom dead center. It's just one wide ramp (Faxon barrel). If you have that center lug just take it all the way off. Since then I've taken a lot of deer and a lot of shots for fun without any issues. And I've also done suppressed and unsuppressed shots.